Conventional subbing chemistry has not proven totally effective on biaxially oriented polyester support, and thus, there is a problem of adhesion in the photoprocessor environment of aqueous coats of photograpic emulsions to these highly inert polymer surfaces. Recent approaches to overcoming the challenges of subbing biaxially oriented polyester support have involved plasma treatments, UV treatments, and other surface modification techniques often combined with heating the support material and/or complicated subbing chemistry. Recent advances in subbing technology have shown promise for replacing a U-coat/gelatin sub system with a single subbing layer applied to a plasma treated biaxially oriented polyester support. This is described in more detail in U.S. Ser. No. 08/199,416, filed Feb. 22, 1994 entitled "Use of Glow Discharge Treatment to Promote Adhesion of Aqueous Coats to Substrate", now U.S. Pat. 5,425,980.
As described in U.S. Ser. No. 08/199,416, filed Feb. 22, 1994, now U.S. Pat. No. 5,425,980, it has been shown that photographic emulsions may adhere to plasma treated support using gelatin sub and no U-coat, a single subbing layer containing a terpolymer and gelatin (as described in U.S. Pat. Nos. 4,695,532 and 4,689,359), or no subbing at all. The plasma treatment technology has enabled the coating of emulsions and gelatin based subbing layers directly onto biaxially oriented polyesters.
In particular, the single subbing layer has shown a wide plasma treatment latitude for obtaining acceptable wet adhesion of emulsion to support. A problem with the single-sub layer, however, has been that the adhesive strength of the emulsion package is somewhat reduced after exposure to photoprocessing chemistry. Alternative approaches involving a gelatin sub and plasma treatment have shown appreciably less latitude than the single-sub chemistry affords. Thus, there is a need to provide a simple and effective process for achieving good wet adhesion of emulsion to biaxially oriented polyester support without sacrificing dry adhesive strength after photoprocessing.
The present invention provides a novel combination of energetic treatment and molecular grafting of amine reactive hardener to a surface of a biaxially oriented polyester support which improves wet adhesion and, in addition, does not lose strength after photoprocessing.